Perspectives and challenges of rechargeable lithium–air batteries

Rechargeable lithium–air batteries have a far higher theoretical energy density than lithium-ion batteries, and are, thus, expected to become a possible power source for electric vehicles (EVs). Three types of rechargeable lithium–air batteries have been developed: non-aqueous, aqueous, and solid. The majority of research efforts have been devoted to the non-aqueous battery in the past two decades. However, non-aqueous lithium–air batteries still have critical issues to be addressed to realize the practical use for EVs, such as a low practical areal capacity, low round-trip energy efficiency, and air purification. The aqueous and solid lithium–air systems do not have the critical issues observed in the non-aqueous system; however, they have not shown capacity for high power density and extended deep cycling. In this short review, our emphasis is on the progress made with respect to cell performance, such as capacity at high current density and cycle life, and we identify lithium–air battery prospects for EVs and key technologies.